Mechanical stability of one-step electrodeposited Ni-graphene superhydrophobic coating

The practical applications of superhydrophobic coatings are limited by their tedious preparation processes and unsatisfactory durability in service environments. This study investigated the mechanical performance of a modification-free Ni-graphene superhydrophobic coating synthesized on mild steel via one-step electrodeposition at a thickness of 7.5 µm. A sandpaper abrasion test and scanning electron microscopy were conducted to verify the mechanical stability of the coating. As the coating possessed dual-roughness structures and the top of the micro-scaled hills exhibited a "sacrificial effect" to maintain the lower part of the hierarchical structure, the water contact angle of the Ni-graphene superhydrophobic coating was maintained above 120° after 1000 cm abrasion on a 400-mesh silicon carbide abrasive paper surface under a pressure of 1.63 kPa. Molecular dynamics simulation of nano-indentation and nano-scratching was conducted to capture the mechanical response dynamically and correlate the atomic structure and macroscopic performance. Through the multi-scaled studies, the mechanical stability of the Ni-graphene superhydrophobic coating was determined by the self-lubricating character of graphene, properties of the coating matrix, and dual-level fractal surface structure.